UNIT 18 SURFACE OF THE EARTH. What features are found on the Earth’s surface? 1. Continents and...
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Transcript of UNIT 18 SURFACE OF THE EARTH. What features are found on the Earth’s surface? 1. Continents and...
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UNIT 18 SURFACE OF THE EARTH
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What features are found on the Earth’s surface?
1. Continents and Islands Continents – 7 large masses of land
- made up of Africa, Antartica,
Asia, Australia, Europe,
North America and South America
- largest continent is Asia Islands – thousands of small land masses
surrounded by water
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The seven continents
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2. Oceans, seas, lakes and rivers 70% of the Earth’s surface is covered by water
surrounding the continents and islands Pacific ocean is the largest and deepest ocean
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3. Mountains and hills Some mountain ranges are found on the ocean floor. Highest point on Earth is Mt. Everest (8848 m above
sea level) in the Himalayas mountain ranges Lowest point on Earth is the Mariana Trench
in the Pacific Ocean (about 11033 m below sea level)
Mount EverestMarianas trench
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4. Other features Plains Volcanoes Valleys Desert – make up 1/3 of the Earth’s land surface
Classified into:
Hot desert – high temperature all year long
Temperate desert – hot summers and freezing
cold winters
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What can change the Earth’s surface?1. Rain
washes away and exposes soil resulting in barren land
acid rain (formed when sulphur dioxide and oxides of nitrogen dissolve in rainwater) removes nutrients from soil, kill aquatic organisms, corrodes and damages buildings
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2. Running water sediments hit against rocks on rivers and grind
against the riverbed and riverbanks rocks loosen and break into pieces by physical
grinding (abrasion) flow of water carries loosened materials away
forming caves and valleys overtime
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3. Wind can pick up small particles of sand, soil and
rocks abrasion by wind particles change shape of
rocks
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4. Sunlight Thermal expansion – expansion of rocks in the day
and contraction at night
- common in areas with large temperature change
such as the desert Frost action – water trapped in rocks may freeze to
become ice and expand causing cracks to enlarge
Thermal expansion Frost action
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5. Tidal waves waves crash onto shores and against cliffs sediments hit and scrape against land surfaces
loosening and smoothening materials outgoing waves carry loosened materials away
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What processes change the Earth’s surface?
1. Slow processes occur over time Include: WEATHERING – physical and chemical break
down of rocks and other land structures Agents are: rain, water, sunlight, tidal waves,
wind EROSION – washing away of soil and rocks Agents are: running water, tidal waves, rain,
wind
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Weathering of rocksErosion of soil
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2. Rapid process
require a very short time for changes to be observable
Include:
LANDSLIDES - movement of rocks down a
slope
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VOLCANIC ERUPTIONS AND EARTHQUAKES
slow plate movements can cause volcanic formation and earthquakes
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How do human activities change the Earth’s surface?
1. Industrialization Factories, power plants and houses Dams Logging Mining Roads and bridges
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dam
logging
mining
bridge
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2. Farming
greater demand for food more land required for better yielding crops
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3. Land reclamation
rocks and other Earth materials are excavated from hills to reclaim land from the sea
needed to build housing for expanding population
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How can we prevent the destruction of the Earth?1. Preventing erosion Do not cut trees unnecessarily Grow trees and plants on exposed soil Keep soil damp during hot weather to lessen
erosion by wind
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2. Preventing landslides
regrow trees and plants on barren slopes do not cut down trees unnecessarily place a wire mesh over rocks and exposed soil
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3. Preventing abrasion
place breakwaters, rocks and concrete along rivers and river banks
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4. Preventing floods
build a strong, thick wall (dyke) along the river
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Sources:
http://pangaeanetwork.org/images/pangaea_map.png http://www.oceania-maps.com/layout/pacific-ocean.gif http://www.ianbrookesphotography.co.uk/images/20081201221946_pb145581.jpg http://glassbox-design.com/wp-content/uploads/2009/01/mariana-trench.jpg http://www.ux1.eiu.edu/~cfjps/1300/heaved.jpg http://web.uct.ac.za/depts/geolsci/dlr/ant/Scan514.jpg http://upload.wikimedia.org/wikipedia/commons/4/41/India_Farming.jpg
BBC world challenge links
http://www.theworldchallenge.co.uk/2010-finalists-project08.php
http://www.theworldchallenge.co.uk/2005-winner.php